JP2015066896A - Multilayered film for use in heat-shrinkable packaging - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayered film for use in heat-shrinkable packaging which can suppress transmission of ultraviolet rays by suppressing bleedout of an ultraviolet absorber and has excellent heat sealability.SOLUTION: There is provided a multilayered film for use in heat-shrinkable packaging which is obtained by laminating a layer A, a layer B and a layer C in this order, wherein the layer A and the layer C contain a polyethylene-based resin, the layer B contains a polyethylene-based resin and comprises 0.1 to 8 pts.mass of an ultraviolet absorber based on 100 pts.mass of the polyethylene-based resin and the average density of the layer B is lower by 0.015 g/cmor more than the average density of both the layer A and the layer C.

Description

  The present invention relates to a multilayer film for heat shrink wrapping.

  Conventionally, corrugated cardboard is used when packaging beverage cans, foods, industrial materials, building members, flooring materials, and the like. When these beverage cans and the like are packaged with cardboard, the weight increases. In recent years, heat shrink wrapping films have been used to reduce the weight.

  The above-mentioned film for heat shrink packaging is used by coloring or protecting it with light such as ultraviolet rays or by adding an ultraviolet absorber (for example, Patent Documents 1 and 2). reference).

JP 2011-51124 A JP 2007-69487 A Japanese Patent No. 2996816

  However, in the above-described method for coloring the packaging film, the total light transmittance of the film due to the coloration is lowered, and the design of the product in the packaged state is lowered. Therefore, the packaging film is required to be transparent. Is done. In addition, in the above-described method of adding an ultraviolet absorber, when used as a heat shrink wrapping film, the ultraviolet absorber bleeds out on the surface of the packaging film, and heat sealability when packaging an object to be packaged. There is a problem of lowering.

  Therefore, it is desired to develop a packaging film that can suppress bleeding out of the ultraviolet absorber, suppress transmission of ultraviolet rays, and is excellent in heat sealability.

  The present invention has been made in view of the above problems, and by suppressing the bleeding out of the ultraviolet absorber, it is possible to suppress the transmission of ultraviolet rays, and heat shrink packaging excellent in heat sealability An object of the present invention is to provide a multilayer film.

As a result of intensive studies to achieve the above object, the present inventors have made a multilayer film for heat shrink packaging in which the A layer, the B layer, and the C layer are laminated in this order. A B-type resin containing a polyethylene-based resin, and 0.1 to 8 parts by mass of an ultraviolet absorber with respect to 100 parts by mass of the polyethylene-based resin, and the average density of the B-layer Was found to be able to achieve the above-described object by lowering the average density of the A layer and the C layer by 0.015 g / cm ³ or more, and the present invention was completed.

That is, this invention relates to the following multilayer film for heat shrink packaging.
1. A multilayer film for heat shrink packaging in which A layer, B layer, and C layer are laminated in this order,
The A layer and the C layer include a polyethylene resin,
The B layer contains a polyethylene resin and contains 0.1 to 8 parts by mass of an ultraviolet absorber with respect to 100 parts by mass of the polyethylene resin.
The average density of the B layer is 0.015 g / cm ³ or less lower than the average density of the A layer and the C layer.
A multilayer film for heat shrink wrapping, characterized by the above.
2. The multilayer film for heat shrink packaging according to Item 1, wherein the ultraviolet absorber is a triazine-based ultraviolet absorber.

The multilayer film for heat-shrink packaging of the present invention (hereinafter sometimes simply referred to as “multilayer film”) has an A layer and a C layer sandwiching the B layer on both sides of the B layer containing an ultraviolet absorber. Are stacked. Moreover, the average density of B layer containing a ultraviolet absorber is 0.015 g / cm < ³ > or less lower than the average density of any of A layer and C layer. For this reason, the ultraviolet absorber contained in B layer becomes difficult to transfer to A layer and C layer with higher average density, and the bleeding out to the multilayer film surface is suppressed. Thereby, when a to-be-packaged object is packaged using the multilayer film for heat shrink packaging of the present invention, the transmission of ultraviolet rays through the multilayer film is suppressed, and the to-be-packaged object can be protected from ultraviolet rays. Moreover, by suppressing the bleed-out of the UV absorber to the surface of the multilayer film, the deterioration of the heat sealability due to the presence of the UV absorber on the surface of the multilayer film is suppressed, and the packaging film having excellent heat sealability. It becomes.

  Hereinafter, the multilayer film for heat shrink packaging of the present invention will be described in detail.

In the heat-shrinkable multilayer film of the present invention, the A layer, the B layer, and the C layer are laminated in this order. The A layer and the C layer include a polyethylene-based resin, and the B layer is a polyethylene-based film. 0.1 to 8 parts by mass of an ultraviolet absorber is contained with respect to 100 parts by mass of the polyethylene-based resin, and the average density of the B layer is any of the average densities of the A and C layers. Is a multilayer film for heat-shrink wrapping that is lower by 0.015 g / cm ³ or more.

(B layer)
The B layer is a layer containing a polyethylene resin, and the polyethylene resin layer is not particularly limited as long as the formed multilayer film can shrink by heat and function as a film for heat shrink packaging. Examples thereof include linear low density polyethylene (LLDPE), low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), and ethylene-α-olefin copolymer. These polyethylene resins may be used alone or in combination of two or more.

  The linear low-density polyethylene can be obtained by copolymerizing ethylene and α-olefin using a single-site catalyst such as a Ziegler catalyst or a metallocene catalyst. The density range can be controlled by adjusting. Examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene and the like. The α-olefin may be used alone or in combination of two or more.

The average density of layer B is 0.015 g / cm ³ or more lower than the average density of layers A and C. It is preferably 0.020 g / cm ³ or lower. By setting the average density of the B layer as described above, bleeding of the ultraviolet absorber to the surface of the multilayer film can be suppressed.

The average density of the B layer is not particularly limited as long as it is 0.015 g / cm ³ or more lower than the average density of the A layer and the C layer, but 0.870 to 0.930 g / cm ³ is preferable, and 0.880 to 0.930 g / cm ³ is more preferable. The average density can be measured by a measuring method based on JIS K7112.

Although it does not specifically limit as a method of adjusting the average density of B layer to the said range, For example, the polyethylene-type resin contained in B-layer and the polyethylene-type resin whose average density is 0.910-0.930 g / cm < ³ >, There is a method of preparing by mixing a polyethylene resin having an average density of 0.870 to 0.910 g / cm ³ and adjusting the blending ratio of these resins as appropriate.

  The ethylene resin preferably has a melt flow rate (MFR) of 0.3 to 5 g / 10 minutes, and more preferably 0.2 to 3 g / 10 minutes. If the MFR of the ethylene-based resin is too small, the film formability of the B layer may be reduced. Moreover, when MFR of ethylene-type resin is too large, there exists a possibility that the mechanical strength of B layer may fall.

  The MFR of the ethylene resin is a melt mass flow rate value measured under the conditions of a temperature of 190 ° C. and a load of 21.18 N by a measuring method in accordance with JIS K7210.

  The B layer contains an ultraviolet absorber (UVA). It does not specifically limit as a ultraviolet absorber, Conventionally well-known things, such as an organic type ultraviolet absorber, can be used. Examples of organic ultraviolet absorbers include triazine ultraviolet absorbers such as triaryltriazine ultraviolet absorbers; 2,2′-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, and the like. Benzophenone UV absorbers; salicylate UV absorbers such as Pt-butylphenyl salicylate; benzoates such as 2,4-di-t-butylphenyl-3,5-di-t-butyl-4-hydroxybenzoate UV absorbers; benzotriazole UV absorbers such as 2- (2′-hydroxy-3 ′, 5′-di-t-amyl-phenyl) benzotriazole; 2,5-bis- [5′-t- And thiophene ultraviolet absorbers such as butylbenzoxazolyl- (2)]-thiophene. Of these, triazine-based ultraviolet absorbers are preferable. A triazine type ultraviolet absorber may be used independently and may be used in mixture of 2 or more types. Moreover, you may use together and use a triazine type ultraviolet absorber and the other ultraviolet absorber.

  Content of the ultraviolet absorber in B layer is 0.1-8 mass parts with respect to 100 mass parts of said polyethylene-type resin. When the content of the ultraviolet absorber is less than 1 part by mass, the transmission of ultraviolet rays cannot be sufficiently suppressed, and when it exceeds 8 parts by mass, the ultraviolet absorber is likely to bleed out. It is preferable that content of a ultraviolet absorber is 1.0-5.0 mass parts.

  Other additives such as a light stabilizer, an antioxidant, a lubricant, and a pigment may be added to the B layer as long as the effects of the present invention are not impaired.

  B layer may be comprised from the single layer and may be comprised from the some layer. When the B layer is composed of a plurality of layers, for example, the B layer has two layers, and the total of the A layer, the B layer, and the C layer has a layer configuration in which the multilayer film for heat shrink packaging of the present invention has five layers Can be mentioned.

(A layer and C layer)
The A layer and the C layer are layers laminated on both sides of the B layer so as to sandwich the B layer.

  The A layer and the C layer contain a polyethylene resin. As a kind of polyethylene resin contained in A layer and C layer, the same thing as the polyethylene resin contained in the said B layer can be used.

The average density of each of the A layer and the C layer is 0.015 g / cm ³ or more higher than the average density of the B layer. It is preferable 0.020 g / cm ³ or more higher, 0.025 g / cm ³ or more higher is more preferable. By setting the average density of each of the A layer and the C layer as described above, bleeding out of the ultraviolet absorber to the surface of the multilayer film can be suppressed. The upper limit of the difference between the respective average densities of A layer and C layer, and the average density of the layer B is not particularly limited, preferably about 0.050 g / cm ^3, more about 0.040 g / cm ³ preferable.

The average density of the A layer and the C layer is not particularly limited as long as it is 0.015 g / cm ³ or more higher than the average density of the B layer, but 0.910 to 0.960 g / cm ³ is preferable, and 0.920 to 0.950 g / cm ³ is more preferable.

  The average density can be measured by a measuring method based on JIS K7112.

  Although it does not specifically limit as a method of adjusting the average density of A layer and C layer to the said range, For example, the polyethylene resin contained in A layer and C layer is 0.940-0.960 high density polyethylene resin And 0.910 to 0.930 of a low density polyethylene resin, and a method of adjusting by appropriately setting the blending ratio of the high density polyethylene resin and the low density polyethylene resin Is mentioned.

  The A layer and the C layer may contain an ultraviolet absorber. The kind of ultraviolet absorber contained in the A layer and the C layer is the same as the ultraviolet absorber used in the B layer. It is preferable that A layer and C layer do not contain an ultraviolet absorber at the point which can suppress the bleed-out of the ultraviolet absorber to the multilayer film surface.

  Other additives such as a light stabilizer, an antioxidant, a lubricant, and a pigment may be added to the A layer and the C layer as long as the effects of the present invention are not impaired.

  15-200 micrometers is preferable and, as for the sum total of the thickness of all the layers of the multilayer film for heat shrink packaging of this invention, 30-100 micrometers is more preferable. If the thickness of the multilayer film is too thin, the transmission of ultraviolet rays may not be sufficiently suppressed, and the mechanical strength of the multilayer film may be reduced. If the thickness of the multilayer film is too thick, it may be difficult to form the multilayer film, and heat sealing may be difficult.

The thickness ratio of each layer constituting the multilayer film for heat shrink according to the present invention is preferably A: B: C = 1: 1: 1 to 1: 6: 1, and 1: 1: 1 to 1: 4: 1 is more preferable. If the A layer and the C layer are too thin, the ultraviolet absorber tends to bleed out, and the transparency and heat sealability of the multilayer film may be reduced. Moreover, when A layer and C layer are too thick, there exists a possibility that the heat-sealing property of a multilayer film may fall.
is there.

(Production method)
It does not specifically limit as a manufacturing method which manufactures the multilayer film for heat-shrink packaging of this invention, Conventionally well-known methods, such as a multilayer inflation method, are mentioned. As the multilayer inflation method, for example, a resin composition in a molten state is prepared by melting and kneading components such as resins constituting each layer in an extruder, and the resin composition is supplied from the extruder to a circular die. The resin composition is coextruded from a circular die to form a cylindrical film, and compressed air is supplied from the center of the circular die, and the formed cylindrical film is circumferentially The method of manufacturing a multilayer film by extending | stretching is mentioned. The inflation method is suitable as a production method for producing the multilayer film of the present invention.

In the multilayer film for heat shrink packaging of the present invention, the A layer, the B layer, and the C layer are laminated in this order, and the average density of the B layer containing the ultraviolet absorber is 0 than the average density of any of the A layer and the C layer. Since it is lower than .015 g / cm ³ , the ultraviolet absorber contained in the B layer is difficult to migrate to the A layer and the C layer having higher average density, and bleed out to the surface of the multilayer film is suppressed. The Thereby, when a package is packaged using the multilayer film for heat shrink packaging of the present invention, the transmission of ultraviolet rays is suppressed, and the package can be protected from ultraviolet rays. In addition, by suppressing the bleed-out of the ultraviolet absorber to the surface of the multilayer film, a decrease in heat sealability due to the presence of the ultraviolet absorber on the surface of the multilayer film is suppressed, and the heat sealability is excellent.

It is sectional drawing which shows the layer structure of the multilayer film for heat shrink packaging of this invention.

(Example)
Examples of the present invention will be described below. The present invention is not limited to the following examples.

Example 1
A multilayer film forming apparatus was prepared in which the tip of the extruder was connected to the same circular die. A low-density polyethylene resin (density 0.922 g / cm ³ , MFR 0.4 g / 10 min, product name “M2204” manufactured by Asahi Kasei Chemical Co., Ltd.) is prepared as a polyethylene resin forming the A layer and the C layer. It melt-kneaded in the 1st extruder and 3rd extruder of a membrane apparatus, and prepared the resin composition for A layer formation, and the resin composition for C layer formation.

As a polyethylene-based resin forming the B layer, 100 parts by mass of an ethylene-α-olefin copolymer (density 0.885 g / cm ³ , MFR 1.0 g / 10 min, trade name “VP8770G1” manufactured by Dow Chemical Co., Ltd.) and ultraviolet absorption 2 parts by weight of a triazine-based UV absorber (trade name “TINUVIN 1577ED” manufactured by BASF) was mixed and melted and kneaded in the second extruder of the multilayer extruder to form a resin composition for forming the B layer. A product was prepared.

  Each of the resin compositions prepared as described above was co-extruded from the first extruder to the third extruder of the multilayer film forming apparatus, so that the A layer, the B layer, and the C layer were laminated in this order. A multilayer film for heat shrink packaging having a thickness of 60 μm was prepared.

Example 2
A multilayer film for heat-shrink packaging was prepared in the same manner as in Example 1 except that the ultraviolet absorber used for the B layer was changed to 2.0 parts by mass of a benzophenone-based ultraviolet absorber (trade name “Kimasorb 81”). .

Example 3
As polyethylene-based resin forming the A layer and the C layer, 50 parts by mass of low density polyethylene (density 0.922 g / cm ³ , MFR 0.4 g / 10 min, product name “M2204” manufactured by Asahi Kasei Chemical Co., Ltd.) and high density polyethylene 50 parts by mass (density 0.952 g / cm ³ , MFR 0.8 g / 10 min, manufactured by Asahi Kasei Chemical Co., Ltd.) were mixed to prepare an A layer forming resin composition and a C layer forming resin composition. In addition, as a polyethylene-based resin forming the B layer, 100 parts by weight of low density polyethylene (density 0.922 g / cm ³ , MFR 0.4 g / 10 min, product name “M2204” manufactured by Asahi Kasei Chemical Co., Ltd.) and an ultraviolet absorber Then, 2 parts by mass of a triazine-based ultraviolet absorber (trade name “TINUVIN 1577ED” manufactured by BASF) was mixed to prepare a resin composition for forming a B layer. Other than that was carried out similarly to Example 1, and produced the multilayer film for heat-shrink packaging.

Example 4
20 parts by mass of low-density polyethylene (density 0.922 g / cm ³ , MFR 0.4 g / 10 min, trade name “M2204” manufactured by Asahi Kasei Chemical Co., Ltd.) as a polyethylene resin forming the A layer and the C layer, and high-density polyethylene 80 parts by mass (density 0.952 g / cm ³ , MFR 0.8 g / 10 min, manufactured by Asahi Kasei Chemical Co., Ltd.) were mixed to prepare an A layer forming resin composition and a C layer forming resin composition. In addition, as a polyethylene-based resin forming the B layer, 100 parts by weight of low density polyethylene (density 0.922 g / cm ³ , MFR 0.4 g / 10 min, product name “M2204” manufactured by Asahi Kasei Chemical Co., Ltd.) and an ultraviolet absorber Then, 2 parts by mass of a triazine-based ultraviolet absorber (trade name “TINUVIN 1577ED” manufactured by BASF) was mixed to prepare a resin composition for forming a B layer. Other than that was carried out similarly to Example 1, and produced the multilayer film for heat-shrink packaging.

Example 5
A multilayer film for heat-shrinkable packaging in the same manner as in Example 1 except that the UV absorber used in the B layer is changed to 8.0 parts by mass of a triazine UV absorber (trade name “TINUVIN 1577ED” manufactured by BASF). Was made.

Example 6
A multilayer film for heat-shrinkable packaging in the same manner as in Example 1 except that the ultraviolet absorber used in the B layer is changed to 0.1 parts by mass of a triazine-based ultraviolet absorber (trade name “TINUVIN 1577ED” manufactured by BASF). Was made.

Comparative Example 1
As polyethylene-based resin forming the B layer, 100 parts by weight of low-density polyethylene (density 0.922 g / cm ³ , MFR 0.4 g / 10 min, trade name “M2204” manufactured by Asahi Kasei Chemical Co., Ltd.) and triazine as an ultraviolet absorber A resin composition for forming a B layer was prepared by mixing 2 parts by mass of a UV absorber (trade name “TINUVIN 1577ED” manufactured by BASF). Other than that was carried out similarly to Example 1, and produced the multilayer film for heat-shrink packaging.

Comparative Example 2
70 parts by mass of low density polyethylene (density 0.922 g / cm ³ , MFR 0.4 g / 10 min, trade name “M2204” manufactured by Asahi Kasei Chemical Co., Ltd.) as a polyethylene resin forming the A layer and the C layer, and high density polyethylene 30 parts by mass (density 0.952 g / cm ³ , MFR 0.8 g / 10 min, manufactured by Asahi Kasei Chemical Co., Ltd.) were mixed to prepare an A layer forming resin composition and a C layer forming resin composition. In addition, as a polyethylene-based resin forming the B layer, 100 parts by weight of low density polyethylene (density 0.922 g / cm ³ , MFR 0.4 g / 10 min, product name “M2204” manufactured by Asahi Kasei Chemical Co., Ltd.) and an ultraviolet absorber Then, 2 parts by mass of a triazine-based ultraviolet absorber (trade name “TINUVIN 1577ED” manufactured by BASF) was mixed to prepare a resin composition for forming a B layer. Other than that was carried out similarly to Example 1, and produced the multilayer film for heat-shrink packaging.

Comparative Example 3
As polyethylene-based resin for forming the B layer, 100 parts by weight of low-density polyethylene (density 0.922 g / cm ³ , MFR 0.4 g / 10 min, trade name “M2204” manufactured by Asahi Kasei Chemical Co., Ltd.) and benzophenone as an ultraviolet absorber A B-layer-forming resin composition was prepared by mixing 2 parts by mass of an ultraviolet absorber (trade name “Kimasorb 81”). Other than that was carried out similarly to Example 1, and produced the multilayer film for heat-shrink packaging.

  The following evaluation was performed about the produced multilayer film for heat-shrink packaging of Examples 1-6 and Comparative Examples 1-3.

<Transparency test> (visual evaluation)
The surface of the obtained multilayer film for heat shrink packaging was rubbed lightly, and the transparency was evaluated according to the following criteria by visual observation.
○: Bleed-out is not seen △: Appears slightly white ×: Appears white over the entire surface

<Transparency test> (Haze difference measurement)
The surface of the obtained multilayer film for heat shrink wrapping was lightly wiped with alcohol, and haze was measured by a method based on JIS K7105. The multilayer film for heat-shrink packaging after the measurement was placed in an incubator at 60 ° C. and 40 RH% for 3 days, and then the haze was measured again. The rate of increase in haze after storage with respect to haze before storage was calculated with the haze before storage as 100% and evaluated according to the following criteria.
○: Less than 5% Δ: 5% or more and less than 10% ×: 10% or more

<Total light transmittance measurement>
The multilayer film for heat shrink packaging was placed in an incubator at 60 ° C. and 40 RH% and stored for 3 days, and then the total light transmittance was measured by a method according to JIS K7105 and evaluated according to the following criteria.
○: 85% or more ×: less than 85%

<Heat seal strength>
The heat seal strength was measured under the measurement conditions of a seal temperature of 150 ° C., a seal time of 1 second, and a seal bar width of 0.5 mm by a measurement method based on JIS K1707, and evaluated according to the following criteria.
○: 9.0N or more ×: less than 9.0N

<Ultraviolet transmittance>
Using a spectrophotometer (Hitachi, product name “U-3000”), the total light transmittance at a wavelength of 350 nm of the produced multilayer film for heat shrink packaging was measured and evaluated according to the following criteria.
○: Less than 40% ×: 40% or more

<Package suitability evaluation>
Using a sleeve packaging machine (product name “S-650LT” manufactured by Nissan Kiko Co., Ltd.), the package was shrink-wrapped, and the finished state was evaluated according to the following criteria.
○: The film heat-shrinks and finishes beautifully. ×: The film does not heat-shrink and finishes in a relaxed state.

  The results are shown in Table 1.

DESCRIPTION OF SYMBOLS 1 ... Multilayer film for heat shrink packaging, 2 ... A layer, 3 ... B layer, 4 ... C layer

Claims (2)

A multilayer film for heat shrink packaging in which A layer, B layer, and C layer are laminated in this order,
The A layer and the C layer include a polyethylene resin,
The B layer contains a polyethylene resin and contains 0.1 to 8 parts by mass of an ultraviolet absorber with respect to 100 parts by mass of the polyethylene resin.
The average density of the B layer is 0.015 g / cm ³ or less lower than the average density of the A layer and the C layer.
A multilayer film for heat shrink wrapping, characterized by the above.   The multilayer film for heat-shrink packaging according to claim 1, wherein the ultraviolet absorber is a triazine-based ultraviolet absorber.

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